
The initially overlooked paper by Zwicky [1]} on the velocity dispersion of galaxies in the Coma cluster led him to postulate additional Dark matter.

On cosmological scales the density of the universe is at the critical density according to observations.The component of visible matter is only \(4\%\)  of the critical density. Other contributions are needed; the dark matter contribution is estimated to be about \(25\%\)  [2]}, [3]}, [4]}.

Dark matter in the early universe is also required for formation of structure in the universe [5]}, [6]}.

